Radar system providing multiple waveforms for long range and short range target detection

ABSTRACT

Various techniques are disclosed for providing a radar system. In one example, such a radar system includes a radar unit adapted to broadcast radar signals and receive return signals in response thereto. The radar unit includes a waveform generator adapted to provide pulse waveforms of different pulse widths and Frequency Modulated Continuous Wave (FMCW) waveforms, wherein the waveforms are interleaved with each other to provide a transmission sequence for the radar signals for detection of long range and short range targets, a power amplifier adapted to amplify the radar signals for broadcast, and an antenna adapted to broadcast the radar signals and receive the return signals. Other examples of radar systems and related methods are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/581,989 filed Dec. 30, 2011 and entitled “RADARSYSTEM PROVIDING MULTIPLE WAVEFORMS FOR LONG RANGE AND SHORT RANGETARGET DETECTION”, which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

One or more embodiments of the invention relate generally to radarsystems and more particularly, for example, to solid state radartechnology.

BACKGROUND

Radar systems are commonly used to detect targets (e.g., objects,geographic features, or other types of targets) in proximity towatercraft, aircraft, vehicles, or fixed locations. Conventional radarsystems typically employ magnetrons to generate radar signals.Unfortunately, magnetrons and their related microwave hardwarearchitecture are often expensive, physically cumbersome, and requirelarge power supplies to operate. As a result, magnetron-based radarsystems may not be well suited for use in compact or portable radarsystems.

Certain radar systems employ rotary joints with one or more waveguidesprovided therein to direct signals between a rotating radar antenna andother components. However, such rotary joints are often complicated todesign, build, and manufacture. As a result, these components cansignificantly increase the cost of their associated radar systems. Inaddition, conventional rotary joints may exhibit rotational noise thatis unintentionally detected by the radar system.

Many existing radar systems use signaling schemes that generally benefitshort range or long range target detection, to the detriment of theother. For example, pulsed radar signaling schemes may provide desirabletarget detection at long ranges. However, the transmitted pulsed radarsignal may obscure the detection of short range return signals. Suchproblems are not preferred, but are often tolerated in pulsed radarsignaling schemes because other long range detection techniquesgenerally have higher power requirements and may require highlyspecified components. Conversely, Frequency Modulated Continuous Wave(FMCW) signaling schemes may provide desirable short range targetdetection, but may not be as effective at providing long range targetdetection.

Various radar systems may be implemented with Mini Automatic RadarPlotting Aid (MARPA) features in which detected targets may be selectedfor tracking. However, existing MARPA implementations are often hamperedby inaccurate target identification. In particular, such implementationsmay incorrectly identify sea clutter as trackable targets and thus mayreduce the accuracy of associated radar systems.

SUMMARY

Various techniques are disclosed for providing a radar system. Forexample, in certain embodiments, such a radar system may be implementedin a cost efficient manner and with a high degree of functionality.

In one embodiment, a radar system may be implemented with a GalliumNitride (GaN) power amplifier to amplify radar signals for broadcast.Such an amplifier may be used, for example, in place of a magnetron topermit the radar system to be implemented with a compact form factor andrelatively low power draw. In another. embodiment, a Gallium Arsenide(GaAs) power amplifier may be used. Other amplifier implementations maybe used in various embodiments where appropriate.

In another embodiment, a radar system may be implemented with a wirelesstransmitter to provide radar data from a rotating antenna to a basestation. Such a wireless transmitter may be used, for example, toprovide radar data without requiring a complicated rotary joint to passdetected signals.

In another embodiment, a radar system may be implemented with asignaling scheme configured to perform pulsed and FMCW signaling in asingle radar system. Such a signaling scheme, for example, may be usedto perform both short range and long range detection using a singleradar system.

In another embodiment, a radar system may be implemented to performDoppler processing on radar return signals to determine velocities ofdetected targets. Such processing, for example, may be used to provideaccurate and reliable vessel target tracking, sea clutter recognition,and assistance in target identification.

In another embodiment, a radar system includes a radar unit adapted tobroadcast radar signals and receive return signals in response thereto,the radar unit comprising: a waveform generator adapted to provide pulsewaveforms of different pulse widths and Frequency Modulated ContinuousWave (FMCW) waveforms, wherein the waveforms are interleaved with eachother to provide a transmission sequence for the radar signals fordetection of long range and short range targets; a power amplifieradapted to amplify the radar signals for broadcast; and an antennaadapted to broadcast the radar signals and receive the return signals.

In another embodiment, a method of operating a radar system includesgenerating radar signals using a waveform generator to provide pulsewaveforms of different pulse widths and Frequency Modulated ContinuousWave (FMCW) waveforms, wherein the waveforms are interleaved with eachother to provide a transmission sequence for the radar signals fordetection of long range and short range targets; amplifying the radarsignals for broadcast using a power amplifier; broadcasting the radarsignals using an antenna; receiving return signals at the antenna inresponse to the radar signals; and wherein the waveform generator, thepower amplifier, and the antenna are part of a radar unit.

The scope of the invention is defined by the claims, which areincorporated into this section by reference. A more completeunderstanding of embodiments of the invention will be afforded to thoseskilled in the art, as well as a realization of additional advantagesthereof, by a consideration of the following detailed description of oneor more embodiments. Reference will be made to the appended sheets ofdrawings that will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a radar system including a radarunit and a base station in accordance with an embodiment of thedisclosure.

FIG. 2 illustrates a perspective view of a radar unit with a cover shownin semi-transparent form to reveal internal components in accordancewith an embodiment of the disclosure.

FIGS. 3 and 4 illustrate perspective views of a radar unit with a coverremoved in accordance with embodiments of the disclosure.

FIG. 5 illustrates a top view of a radar unit with a cover removed inaccordance with an embodiment of the disclosure.

FIG. 6 illustrates a front view of a radar unit with a cover removed inaccordance with an embodiment of the disclosure.

FIG. 7 illustrates a cross sectional view of a radar unit with a coverremoved taken along lines 7-7 of FIG. 5 in accordance with an embodimentof the disclosure.

FIG. 8 illustrates a cross sectional view of a radar unit taken alonglines 8-8 of FIG. 6 in accordance with an embodiment of the disclosure.

FIG. 9A illustrates a block diagram of a radar unit in accordance withan embodiment of the disclosure.

FIG. 9B illustrates another block diagram of a radar unit in accordancewith an embodiment of the disclosure.

FIG. 10 illustrates yet another block diagram of a radar unit inaccordance with an embodiment of the disclosure.

FIG. 11 illustrates timing diagrams of a radar unit in accordance withan embodiment of the disclosure.

FIG. 12 illustrates a process of operating a radar system in accordancewith an embodiment of the disclosure.

FIG. 13 illustrates a further block diagram of a radar unit inaccordance with an embodiment of the disclosure.

Embodiments of the invention and their advantages are best understood byreferring to the detailed description that follows. It should beappreciated that like reference numerals are used to identify likeelements illustrated in one or more of the figures.

DETAILED DESCRIPTION

FIG. 1 illustrates a block diagram of a radar system 100 including aradar unit 110 and a base station 111 in accordance with an embodimentof the disclosure. In various embodiments, radar system 100 may beconfigured for use on watercraft, aircraft, vehicles, fixed locations,or other environments, and may be used for various applications such as,for example, leisure navigation, commercial navigation, militarynavigation, other types of navigation, or other applications. In oneembodiment, radar unit 110 may be implemented as a relatively compactportable unit that may be conveniently installed by a user.

As further described herein, radar unit 110 may be implemented tobroadcast radar signals 105 and receive reflected return signals 108 inresponse thereto. Radar unit 110 may be in wireless communication withbase station 111 through wireless signals 109 to provide, for example,radar data to base station 111 corresponding to return signals 108. Suchwireless communication may be implemented in accordance with variouswireless technology including, for example, Wi-Fi™, Bluetooth™, or otherstandardized or proprietary wireless communication techniques.

Base station 111 may be used to receive, process, and display radar datareceived from radar unit 110. In one embodiment, base station 111 may beinstalled at a fixed location. In another embodiment, base station 111may be a portable device, such as a personal electronic device (e.g., acell phone, personal digital assistant, laptop computer, camera, orother device). In one embodiment, base station 111 may operate as acontrol unit to provide control signals to radar unit 110 throughwireless signals 109 to control the operation of radar unit 110. Basestation 111 includes a communication interface 101, a processor 102, amemory 103, a machine readable medium 104, a display 106, and othercomponents 107.

Communication interface 101 may communicate with radar unit 110 through,for example, wireless signals 109 and/or wired signals (e.g., passed byEthernet and/or other wired communication mediums). Processor 102 may beimplemented as any appropriate processing device (e.g., microcontroller,processor, application specific integrated circuit (ASIC), logic device,field programmable gate array (FPGA), circuit, or other device) that maybe used by base station 110 to execute appropriate instructions, such asnon-transitory machine readable instructions (e.g., software) stored onmachine readable medium 104 and loaded into memory 103. For example,processor 102 may be configured to receive, process, or otherwisemanipulate radar data received by communication interface 101, store theresults in memory 103, and provide the results to display 106 forpresentation to a user.

Display 106 may be used to present radar data, images, or informationreceived or processed by base station 111. For example, in oneembodiment, display 106 may be viewable by a user of radar system 100.In one embodiment, display 106 may be a multifunction display with atouchscreen configured to receive user inputs to control base station111.

Base station 111 may include various other components 107 that may beused to implement other features such as, for example, other usercontrols, communication with other devices, or other components. Forexample, in one embodiment, communication interface 101 may communicatewith another device which may be implemented with some or all of thefeatures of base station 111.

Such communication may be performed through appropriate wired orwireless signals (e.g., Wi-Fi™,Bluetooth™, or other standardized orproprietary wireless communication techniques). For example, basestation 111 may be located at a first position (e.g., on a bridge of awatercraft in one embodiment) and may communicate with a personalelectronic device (e.g., a cell phone in one embodiment) located at asecond position (e.g., co-located with a user on another location on thewatercraft). In this regard, the user's personal electronic device mayreceive radar data and/or other information from base station 111 and/orradar unit 110. As a result, a user may conveniently receive relevantinformation (e.g., radar images, alerts, or other information) evenwhile not in proximity to base station 111.

In various embodiments, one or more components of base station 111 maybe implemented in radar unit 110. In one embodiment, operationsdescribed herein as being performed by processor 102 may be performed byan appropriate processor and related components of radar unit 110, andvice versa.

FIGS. 2-8 illustrate various views of radar unit 110. Specifically, FIG.2 illustrates a perspective view of radar unit 110 with a cover 112shown in semi-transparent form to reveal internal components inaccordance with an embodiment of the disclosure. FIGS. 3 and 4illustrate perspective views of radar unit 110 with cover 112 removed inaccordance with embodiments of the disclosure. FIG. 5 illustrates a topview of radar unit 110 with cover 112 removed in accordance with anembodiment of the disclosure. FIG. 6 illustrates a front view of radarunit 110 with cover 112 removed in accordance with an embodiment of thedisclosure. FIG. 7 illustrates a cross sectional view of radar unit 110with cover 112 removed taken along lines 7-7 of FIG. 5 in accordancewith an embodiment of the disclosure. FIG. 8 illustrates a crosssectional view of radar unit 110 taken along lines 8-8 of FIG. 6 inaccordance with an embodiment of the disclosure.

Referring now to FIGS. 2-8, radar unit 110 includes a main assembly 150mounted to a base 114 through a coupling 134 and enclosed by cover 112.In one embodiment, cover 112 and base 114 may be molded components.

Main assembly 150 includes a radar flare 116, a front plate 118, aheatsink 120, a receiver printed circuit board (PCB) 122, a receivercover 124, a wireless interface 125 (e.g., a transmission interface), apower cover 126, a circulator 127, a power PCB 128, a patch antenna 130,a low noise converter PCB 132, slip rings 136, ball bearings 140, amotor 142 (e.g., an electric motor in one embodiment), a drive bush 144,and a main support 148.

Main assembly 150 may be configured to rotate relative to base 114. Inthis regard, drive bush 144 may contact or otherwise engage a track 146of base 114 and motor 142. In one embodiment, track 146 may be asubstantially circular track encircling an axis of rotation of mainassembly 150 (e.g., the axis of rotation may correspond to coupling134). In this regard, track 146 may be positioned near a perimeter(e.g., an outside edge) of main assembly 150 and away from coupling 134.Motor 142 and/or drive bush 144 may be positioned substantially neartrack 146 to permit drive bush 144 to contact or otherwise engage withtrack 146. In operation, motor 142 may cause drive bush 144 to rotateagainst track 146 and thus cause main assembly 150 to rotate relative tobase 114 using ball bearings 140. As a result, patch antenna 130 mayrotate with the rest of main assembly 150 to transmit radar signals 105and detect return signals 108 over a 360 degree range of rotation.

Slip rings 136 may receive electrical power from a power source (e.g., abattery, generator, engine, or other power source) external to radarunit 110, and pass the electrical power to various electrically poweredcomponents of main assembly 150. As a result, main assembly 150 may bepowered while it rotates relative to base 114. In another embodiment,radar unit 110 may include a rechargeable power source (e.g., a batteryprovided on or connected to power PCB 128 in one embodiment) to permit auser to charge up radar unit 110 before or after installation on awatercraft or other location. Other power sources may be used in otherembodiments.

Main support 148 may be used to provide a physical mounting structurefor the various components of main assembly 150. For example, radarflare 116, patch antenna 130, and low noise converter PCB 132 may bemounted to front plate 118 which may be mounted to main support 148.

Patch antenna 130 may transmit radar signals 105 and receive returnsignals 108. Radar flare 116 may direct the transmitted radar signals105 and the received return signals 108. Heatsink 120 may dissipate heatgenerated by radar unit 110.

Power PCB 128 may be used to provide various components for amplifyingradar signals 105 and for distributing power to radar unit 110. Forexample, in one embodiment, power PCB 128 may receive electrical powerthrough slip rings 136. In another embodiment, power PCB 128 may includea power source, such as a rechargeable battery or other power source.

Receiver PCB 122 and low noise converter PCB 132 may provide variouscomponents to amplify and/or convert return signals 108 for use by radarunit 110.

In one embodiment, the various components of radar unit 110 may beimplemented in a non-hermetically sealed arrangement. Receiver cover 124and power cover 126 may be used to protect receiver PCB 128 and powerPCB 128, respectively, from environmental conditions.

Wireless interface 125 may be used to communicate with communicationinterface 101 through wireless signals 109 to provide, for example,radar data to base station 111 corresponding to return signals 108 asdiscussed. Advantageously, the use of wireless interface 125 may permitradar unit 110 to be implemented without a complicated rotary joint(e.g., without one or more waveguides or data communication cables suchas Ethernet cables or other cables connected to base station 111). Forexample, in one embodiment, radar unit 110 may not receive any wired orwaveguided signal communications, and may only receive electrical powerthrough slip rings 136. In another embodiment, radar unit 110 mayinclude a power source and may receive no external electrical power, andno wired or waveguided signal communications.

In some embodiments, any type of transmission interface such as a wiredinterface (e.g., Ethernet and/or others) a wireless interface, and/orcombinations of wired and wireless interfaces may be used in place of orin addition to perform the various operations of wireless interface 125.

Circulator 127 may be used to selectively direct radar signals 105 andreturn signals 108 to or from patch antenna 130. In one embodiment,circulator 127 may be a surface mount circulator configured to bemounted on a rear side of radar unit 110. Other types of circulators maybe used in other embodiments.

FIG. 9A illustrates a block diagram 900 of radar unit 110 in accordancewith an embodiment of the disclosure. Block diagram 900 identifiescomponents that may be used to provide various features of radar unit110 in one embodiment. The various components identified in blockdiagram 900 may be implemented by any of the circuit boards or othercomponents of radar unit 110 identified in FIGS. 2-8 and 10.

Block diagram 900 includes a waveform generator 910, amplifiers 930,932, and 940, a band pass filter 950, a circulator 960, an antenna 970,a band pass filter 980, a limiter 982, and a downconverter 990. Variouscontrol signals 915, 917, 933, and 947 may be provided by one or morecontrol units to adjust the operation of various components of radarunit 110. In one embodiment, base station 110, or another device incommunication with base station 111 or radar unit 110, may operate assuch a control unit (e.g., one or more control signals may be generatedby base station 111 and provided to radar unit 110 through wirelesssignals 109 or appropriate wired communications). In another embodiment,appropriate components of radar unit 110 may operate as such a controlunit.

Waveform generator 910 provides various waveforms, such as pulses ofvarious lengths (e.g., different pulse widths), and FMCW signals, whichmay be implemented in radar signals 105. For example, long and shortpulse waveforms may be generated for long range target detection. Asanother example, FMCW signals (e.g., linear frequency varying signalsalso referred to as chirp signals) may be generated for short rangetarget detection. Such FMCW signals may be implemented, for example, asrising, falling, or rising/falling frequency sweeps (e.g., upchirps,downchirps, or up/down chirps). Other types of pulses, FMCW signals, andother waveforms may be used in other embodiments.

Waveform generator 910 includes a reference signal generator 912, adirect digital synthesizer (DDS) 914, a phase locked loop (PLL) circuit916, an oscillator 918, a coupler 920, and an upconverter 922. Referencesignal generator 912 (e.g., a crystal oscillator in one embodiment)generates a reference signal 913 (e.g., a 10 MHz reference signal in oneembodiment) that is provided to DDS 914 and PLL circuit 916.

DDS 914 provides a baseband signal 919 (e.g., in the form of I and Qsignals in one embodiment). In one embodiment, baseband signal 919 mayhave a nominal frequency of 40 MHz with an additional frequencydeviation of up to 32 MHz (e.g., to provide a frequency range from 40MHz to 72 MHz). In one embodiment, the frequency deviation and pulselength of baseband signal 919 may be varied with a range setting ofradar unit 110 in response to control signal 915 (e.g., such that whenradar unit 110 is set to the minimum range, radar signals 105 are nomore than 5 percent of a displayed range scale when transmitted). In oneembodiment, DDS 914 may be implemented by a FPGA and digital to analogconverters (DACs). DDS 914 is clocked by reference signal 913 tomaintain phase coherence between multiple radar pulses provided by radarsignals 105.

PLL circuit 916 operates with oscillator 918 (e.g., running at 9.36 GHzin one embodiment) to provide a local oscillator (LO) signal 923 (e.g.,a microwave X-band signal such as a 9.36 GHz signal in one embodiment)based on reference signal 913 and control signal 917. LO signal 923 isreceived by upconverter 922 through coupler 920.

Upconverter 922 translates baseband signal 919 to the X-band frequencyrange to provide an upconverted signal 925. In one embodiment,upconverted signal 925 may be an X-band signal within the maritime radarmicrowave signal range of 9.3 GHz to 9.5 GHz. In one embodiment,upconverter 922 may be implemented as an I/Q upconverter (e.g., a singlesideband mixer) to comply with International Telecommunication Union(ITU) spectrum emission standards, or other standards. In oneembodiment, the use of I and Q signals for baseband signal 919 maysuppress an undesired sideband by up to 50 dB. In one embodiment,upconverted signal 925 may have a frequency range of 9.36 GHz to 9.4 GHz(e.g., corresponding to the 9.36 GHz frequency of the LO signal 923swept by the 32 MHz frequency deviation of baseband signal 919).

Upconverted signal 925 is amplified by amplifiers 930, 932, and 940 toprovide radar signal 105. In one embodiment, amplifier 930 may be afixed gain amplifier.

In one embodiment, amplifier 932 may be a variable gain amplifier (e.g.,having approximately 30 dB of wideband gain in one embodiment) that maybe rapidly adjusted in response to one or more control signals 933(e.g., amplitude modulation (AM) signals in one embodiment) to defineand control the rise and fall times of transmitted radar pulses (e.g.,corresponding to the waveforms provided by waveform generator 910) toreduce range side lobes (e.g., associated with pulse compressiontechniques) and to limit the transmitted spectrum profile to comply withITU spectrum emission standards, or other standards. In one embodiment,the gain control provided by amplifier 932 may be augmented or replacedby an FPGA of waveform generator 910 controlling the output of DDS 914.

In one embodiment, amplifier 940 may include one or more drivers 942,944, and 946 which may be implemented by one or more GaN field effecttransistors (FETs) in one or more stages to provide compact andefficient amplification based on one or more control signals 947 (e.g.,bias switching signals in one embodiment). Accordingly, amplifier 940may also be referred to as a power amplifier. In one embodiment,amplifier 940 may be implemented as a two or three stage GaN device on aceramic substrate with a matching circuit. In one embodiment, amplifier940 may be implemented using multiple integrated circuits (e.g., amultiple chip module) using a GaN high electron mobility transistor(HENT) die with GaN and/or GaAs drivers. In one embodiment, amplifier940 may be matched to 50 Ohms nominally at its input and output.

In one embodiment, by implementing amplifier 940 as a solid state GaNdevice, radar system 100 may exhibit increased manufacturing yields,increased lifespan, decreased warm up times, increased power efficiency(e.g., greater than 35 percent per stage), reduced size and weight(e.g., more than 100 times lighter in one embodiment), reduced peakpower, reduced power consumption, reduced spurious radio frequency (RF)emissions, and reduced cost in comparison with conventionalmagnetron-based systems. As discussed, GaAs and other amplifierimplementations are also contemplated.

In one embodiment, amplifier 940 operates over the marine radartransmission band of 9.3 GHz to 9.5 GHz, with a nominal peak output of20 Watts or greater and over 20 dB of gain from an input level of +15dBm. In one embodiment, radar unit 110 may include additional filters(e.g., as part of or separate from amplifier 940) to filter undesiredsignals and harmonics (e.g., second and third harmonics of amplifier940).

In one embodiment, amplifier 940 operates at a low duty cycle (e.g.,less than 5 percent or less than 10 percent in various embodiments),rather than a continuous wave implementation. By using a low duty cycle,amplifier 940 may exhibit reduced average power dissipation, may bepackaged at low cost, and may exhibit improved thermal efficiency overother systems (e.g., approximately a 10 times improvement over somemagnetron-based systems and approximately a 2 times improvement oversome Gallium Arsenide (GaAs) based systems in various embodiments).

In one embodiment, drain and gate bias current for each stage ofamplifier 940 may be switched in response to control signals 947 and insympathy with (e.g., in relation to or synchronous with to some extent)the waveforms provided by waveform generator 910 such that amplifier 940is off (e.g., exhibits minimum gain and maximum isolation) when nowaveforms for radar signals 105 are desired to be transmitted (e.g., toprevent carrier signal leakage from overloading receive components ofradar unit 110 when no desired signal is present).

Band pass filter 950 filters radar signal 105 to attenuate any unwantedfrequencies outside the designated marine radar transmit band. In oneembodiment, band pass filter 950 may be implemented as a micro-stripcoupled filter. Circulator 960 (e.g., which may be used to implementcirculator 127 in one embodiment) selectively directs radar signals 105and return signals 108 to or from antenna 970 (e.g., which may be usedto implement patch antenna 130 in one embodiment). Band pass filter 980filters return signals 108 to attenuate any unwanted frequencies outsidethe designated marine radar transmit band.

In one embodiment, amplifier 940, circulator 960, and various othercomponents of radar system 110 may be implemented as low power surfacemount components (e.g., with connection terminals co-planar to theunderside of the components to permit automated assembly, rather thanusing a drop-in package style, flange mounting, or chips with wirebonding). In this regard, the underside of such components may provideground and heat sink surfaces suitable for solder attachment to one ormore PCBs and to dissipate heat to such PCBs.

Limiter 982 limits the amplitude of return signals 108. For example,limiter 982 may prevent radar signals 105 from overloading downstreamcircuitry in the event that radar signals 105 (e.g., having a muchgreater amplitude than return signals 108) are inadvertently detected byantenna 970 (e.g., resulting from leakage occurring during transmissionof radar signals 105). Limiter 982 may also prevent similar overloadingfrom other signals such as, for example, other conventional pulse radarsignals that may be in the vicinity of radar unit 110. In oneembodiment, limiter 982 may be implemented using one or more diodes.

Downconverter 990 converts return signals 108 to I and Q signals 991(e.g., also referred to as data signals) at intermediate frequencies(IF) for further processing. Downcoverter includes amplifiers 992, 994,and 996, a buffer 998, and a mixer 999. In one embodiment, amplifiers992 and 996 may be fixed gain amplifiers, and amplifier 994 may be avariable gain amplifier.

Amplifiers 992, 994, and 996 amplify return signals 108, and buffer 998receives LO signal 923 from coupler 920. Mixer 999 operates on returnsignals 108 and LO signal 923 to downconvert return signals 108 toprovide I and Q signals 991 in the range of 40 MHz to 72 MHz.

By using LO signal 923 in upconverter 922 and downconverter 990, theymay be synchronized and maintain phase coherence with each other. In oneembodiment, such phase coherence improves the processing gain and signalto noise ratio that may be achieved in digital signal processing of Iand Q signals 991.

In one embodiment, non-zero frequencies may be used for I and Q signals991 to eliminate DC offset problems while also allowing I and Q signals991 to be sampled at relatively low frequencies by appropriate analog todigital converters (ADCs) (not shown) which may be provided after theoutput of downconverter 990. In this regard, I and Q signals 991 may besampled and further processed by appropriate components of radar unit110 or base station 111. In one embodiment, I and Q signals 991 (e.g.,or one or more signals derived or sampled therefrom) may be transmittedfrom wireless interface 125 of radar unit 110 to communication interface101 of base station 111 through wireless signals 109.

In FIG. 9A, PLL circuit 916 and oscillator 918 feed upconverter 922 viacoupler 920. In some embodiments, such an arrangement may rely on DSS914 to provide pulse waveforms and FMCW waveforms, and may rely on PLLcircuit 916 and oscillator 918 to provide LO signal 923 used byupconverter 922 to upconvert the waveforms provided by DSS 914.

FIG. 9B illustrates another block diagram 901 of radar unit 110 inaccordance with an embodiment of the disclosure. As shown, variouscomponents illustrated in block diagram 901 may be implemented in thesame, similar, and/or different manner as illustrated in block diagram900 of FIG. 9A. In some embodiments, waveform generator 910 may beimplemented with additional features in FIG. 9B.

In some embodiments, DSS 914 may be used to provide pulse waveforms inbaseband signal 919 that are upconverted to signal 922 (e.g., during apulse operation mode), and PLL circuit 916 and oscillator 918 may beused to provide FMCW waveforms in LO signal 923 (e.g., by sweeping thefrequency of LO signal 923 based on changes in control signal 917) thatare upconverted to signal 922 (e.g., during an FMCW operation mode). Insuch embodiments, the different types of waveforms may be independentlyprovided by DDS 914 and PLL circuit/oscillator 916/918.

In some embodiments, during a pulse operation mode, DSS 914 may providepulse waveforms in baseband signal 919, and PLL circuit/oscillator916/918 may provide a substantially fixed frequency for LO signal 923.

In some embodiments, during an FMCW operation mode, DSS 914 may be usedsimultaneously with PLL circuit 916 and oscillator 918 to provide FMCWwaveforms in upconverted signal 925. For example, DSS 914 may provide asubstantially fixed frequency (e.g., approximately 32 MHz in oneembodiment) for baseband signal 919, and PLL circuit/oscillator 916/918may sweep the frequency of LO signal 923. As a result, upconvertedsignal 925 may exhibit an FMCW waveform (e.g. associated with the sweepof LO signal 919). As shown, mixer 999 of downconverter 990 receives LOsignal 923 which may be used to downconvert reflected return signals 108to I and Q signals 991 (e.g., intermediate frequency signals).Accordingly, in some embodiments, I and Q signals 991 may be centeredaround the substantially fixed frequency provided by DSS 914 (e.g.,approximately 32 MHz in one embodiment).

In some embodiments, such an approach may reduce receiver-side flickernoise over other approaches where I and Q signals 991 may be centeredsubstantially around 0 MHz. In some embodiments, such an approach mayalso reduce the frequency span, and thus the sample rate used for I andQ signals 919 and/or 991 in comparison with other approaches in whichFMCW signals are provided only by a modulated baseband signal 919 fromDDS 914. In some embodiments, such an approach may also permit basebandsignal 919 to be generated from DDS 914, directly from a DAC (e.g., asidentified in FIG. 9B), and/or any other appropriate type of basebandsignal generator.

FIG. 10 illustrates yet another block diagram 1000 of radar unit 110 inaccordance with an embodiment of the disclosure. Block diagram 1000identifies components that may be used to provide various features ofradar unit 110 in one embodiment. The various components identified inblock diagram 1000 may be implemented by any of the circuit boards orother components of radar unit 110 identified in FIGS. 2-9B.

Block diagram 1000 includes amplifiers 1030, 1032, and 1040, a biasboard 1042, a circulator 1060, a limiter 1082, an amplifier 1084, a biasboard 1086, a motor 1088, and a downconverter 1090.

Amplifiers 1030, 1032, and 1040 may be used to implement amplifiers 930,932, and 940, respectively, of FIG. 9A. In one embodiment, amplifier1030 receives upconverted signal 925 (e.g., from waveform generator 910of FIG. 9A), and amplifier 1040 provides radar signals 105 to circulator1060 (e.g., in one embodiment, radar signals 105 may be further filteredas identified in FIG. 9A).

Bias control board 1042 may operate as a control unit to provide controlsignals 1031, 933, and 947 to amplifiers 1030, 1032, and 1040. Powersignals 1044 (e.g., provided by an appropriate power source internal orexternal to radar unit 110) supply electrical power to amplifier 1040and/or other components of radar unit 110 through slip rings 136. Motor1088 may be used to implement motor 142 in one embodiment.

Circulator 1060, limiter 1082, and downconverter 1090 may be used toimplement circulator 960, limiter 982, and downconverter 990,respectively, of FIG. 9A. In one embodiment, circulator 1060 receivesreturn signals 108 from an antenna (e.g., patch antenna 130 or antenna970 in various embodiments) and passes return signals 108 to limiter1082. In one embodiment, return signals 108 may be further filtered asidentified in FIG. 9A. Limiter 1082 provides return signals 108 todownconverter 1090.

Downconverter 1090 provides I and Q signals 991. Downconverter 1090receives LO signal 923 as discussed with regard to FIG. 9A. Amplifier1084 and bias board 1086 control the operation of downconverter 1090through a bias signal 1087 in response to a gain control signal 1085.

FIG. 13 illustrates a further block diagram 1300 of radar unit 110 inaccordance with an embodiment of the disclosure. In block diagram 1300,circulators 127/960/1060 have been replaced by single pole double throw(SPDT) switches 962/964 (e.g., transmit/receive switches) and adirectional coupler 966. Switches 962/964 may be operated by actuatorsor other appropriate mechanisms as desired. In various embodiments, aconfiguration using switches 962/964 and directional coupler 966 mayprovide improved performance and/or reduced cost over circulator-basedimplementations and still be compatible with pulse compression and FMCWsignaling techniques. Switches 962/964 and directional coupler 966 maybe used in place of or in addition to circulators 127/960/1060 invarious embodiments. Accordingly, any desired type of signal directingdevice (e.g., any combination of circulators 127/960/1060, switches962/964, directional coupler 966, and/or other appropriate components)may be used as desired in particular implementations.

FIG. 11 illustrates timing diagrams 1110 and 1112 of radar unit 110 inaccordance with an embodiment of the disclosure. As discussed, waveformgenerator 910 provides various waveforms, such as pulses of variouslengths and FMCW waveforms, which may be implemented in radar signals105.

Timing diagram 1110 illustrates an example of a transmission sequence inwhich radar signals 105 are transmitted over time periods 1120 to 1142with various types of waveforms. Timing diagram 1112 illustrates anexample of a detection (e.g., listening) sequence in which radar unit110 may detect return signals 108 in response to the transmissionsequence of timing diagram 1110.

During time periods 1120, 1124, 1136, and 1140, radar signals 105 aretransmitted with short pulse (s) waveforms. During time period 1128,radar signals 105 are transmitted with long pulse (I) waveforms.

Time periods 1120, 1124, 1128, 1136, and 1140 are also referred to asmain bang (mb) periods and transmission periods. During the main bangperiods, radar unit 110 may transmit high amplitude pulsed radar signals105 (e.g., having short or long pulses) which are effective fordetection of long range targets. However, during transmission, the highamplitude pulsed radar signals 105 may obscure the reception of anyreturn signals 108. Accordingly, during the main bang periods (e.g., andshortly thereafter in one embodiment), radar unit 110 may not detect anyreturn signals 108.

Following time periods 1120, 1124, 1128, 1136, and 1140, radar unit 110enters corresponding detection periods 1122, 1126, 1130, 1138, and 1142in which return signals 108 are detected in response to the varioustransmitted short and long pulse waveforms.

During time period 1132, radar signals 105 with FMCW waveforms arerepeatedly transmitted and corresponding return signals 108 aredetected. In one embodiment, the FMCW waveform radar signals 105 may bebroadcast with a lower amplitude than the pulsed waveforms providedduring other time periods. Such FMCW signaling techniques are effectivefor detection of short range targets. In one embodiment, radar unit 110may rapidly switch between FMCW transmission and reception during timeperiod 1132 to provide a series of short transmission and detectionperiods within time period 1132.

Following time period 1132, radar unit 110 enters time period 1134(e.g., an interrupted FMCW detection period) during which radar unit 110refrains from transmitting further radar signals 105 but continues todetect return signals 108 in response to previously transmitted lowamplitude FMCW radar signals 105.

As shown in FIG. 11, the different short pulse, long pulse, and FMCWwaveforms may be interleaved with each other over time and may repeat(e.g., the illustrated sequence of short pulse waveform, short pulsewaveform, long pulse waveform, and FMCW waveform may repeat beginningwith the short pulse waveforms shown on the right side of timing diagram1110). Other transmission period sequences may be used in otherembodiments.

By transmitting various pulsed and FMCW radar signals 105, and bydetecting the resulting return signals 108, radar unit 110 may be usedto perform both long range target detection (e.g., detection of largetargets such as land masses, large cruising ships, or other targets at arange of up to approximately 12 nautical miles or more in oneembodiment) and short range target detection (e.g., high resolutiondetection at a range of up to approximately 6 nautical miles or more inone embodiment). Moreover, such detection may be performed with lowerpeak power use in comparison with conventional pulsed signal radarsystems.

The various return signals 108 may be processed and/or combined (e.g.,by processor 102 in one embodiment) in accordance with pulse compressiontechniques, Doppler processing techniques, and/or other techniques, toprovide one or more composite images or target buffers. In oneembodiment, the interleaving of different short pulse, long pulse, andFMCW radar signals 105 permits return signals 108 to be correlated toparticular transmitted radar signals 105, permits Doppler signals to beeffectively identified, and permits resolution of range velocityambiguities associated with detected targets.

Although particular examples of transmission and detection periodsequences and waveforms are shown in FIG. 11, other transmission anddetection period sequences and waveforms may be used in otherembodiments. Moreover, the pulse repetition frequency (PRF) and pulserepetition interval (PRI) associated with the various time periodsidentified in FIG. 11 may be adjusted as desired for particularimplementations.

FIG. 12 illustrates a process of operating radar system 100 inaccordance with an embodiment of the disclosure. Although various blocksof FIG. 12 are primarily described as being performed by either radarunit 110 or base station 111, other embodiments are also contemplatedwherein the various blocks may be performed by any desired combinationof radar unit 110, base station 111, and/or other components.

In block 1210, in an embodiment where radar unit 110 is battery poweredand detachable from its installation location, radar unit 110 may becharged. For example, if radar unit 110 is equipped with a rechargeablepower source, such as a rechargeable battery, then radar unit 110 may becharged before use. In another embodiment, radar unit 110 need not becharged and block 1210 may be omitted.

In block 1220, radar unit 110 is installed for operation. For example,in one embodiment, radar unit 110 may be a portable unit that may beinstalled on watercraft, aircraft, vehicles, or fixed locations. In anembodiment where radar unit 110 receives electrical power from anexternal power source, then block 1220 may include connecting the powersource to radar unit 110 to provide electrical power through slip rings136.

In block 1230, radar unit 110 may be configured for operation. Suchconfiguration may include, for example, setting one or more rangeparameters or other operational parameters of radar unit 110. In oneembodiment, such configuration may be performed by manipulating one ormore physical controls on radar unit 110. In another embodiment, suchconfiguration may be performed by a user interacting with base station111 which sends configuration information to radar unit 110 throughwireless signals 109.

In block 1240, radar unit 110 is activated for operation. As a result,in block 1250, radar unit 110 generates and transmits radar signals 105.In one embodiment, radar signals 105 may be transmitted in accordancewith various pulsed and FMCW waveforms described herein. Other types ofradar signals 105 and other waveforms may be used in other embodiments.

In block 1260, radar unit 110 detects return signals 108. In oneembodiment, return signals 108 may be detected in accordance withvarious pulsed and FMCW detection periods described herein. Other typesof return signals 108 and other detection periods may be used in otherembodiments.

In block 1270, radar unit 110 provides radar data based on returnsignals 108 to base station 111. In one embodiment, such data may besampled I and Q signals 991 that are transmitted from wireless interface125 of radar unit 110 to communication interface 101 of base station 111through wireless signals 109. In another embodiment, such radar data maybe other signals provided by wireless or wired communication betweenradar unit 110 and base station 111.

In block 1280, the data provided in block 1270 is processed by anydesired combination of radar unit 110, base station 111, and/or othercomponents. In one embodiment, such processing may include, for example,pulse compression processing, Doppler processing, MARPA processing,and/or other processing techniques to generate result information in theform of images, text, and/or other forms. In one embodiment, byperforming Doppler processing, radar system 100 may determine thevelocity of detected targets to provide situational awareness for theuser. In one embodiment, radar system 100 may be configured to provideMARPA features to permit accurate and reliable identification andtracking of detected targets (e.g., using velocity vectors in oneembodiment), sea clutter recognition, and sea clutter suppression. SuchMARPA features may be enhanced to perform automatic target acquisition.

In block 1290, the generated result information is displayed to theuser. In one embodiment, the result information is provided on display106 of base station 111. For example, in one embodiment, moving targetsmay be displayed in different colors to depict closing or retreatingtargets.

In view of the present disclosure, it will be appreciated that a radarsystem 100 implemented in accordance with the various embodimentsidentified herein may provide various advantages over conventional radarsystems. For example, the use of a solid state GaN amplifier in place ofa magnetron permits radar system 100 to be implemented with a compactform factor and relatively low power draw. As another example, the useof wireless interface 125 permits radar system 100 to be implementedwithout a complicated rotary joint to pass return signals 108. Asanother example, the use of both pulsed and FMCW signaling permits radarsystem 100 to perform both short range and long range detection using asingle radar system. As another example, radar system 100 may performDoppler processing on return signals 108 to provide accurate andreliable vessel target tracking, sea clutter recognition, and assistancein target identification.

Where applicable, various embodiments provided by the present disclosurecan be implemented using hardware, software, or combinations of hardwareand software. Also where applicable, the various hardware componentsand/or software components set forth herein can be combined intocomposite components comprising software, hardware, and/or both withoutdeparting from the spirit of the present disclosure. Where applicable,the various hardware components and/or software components set forthherein can be separated into sub-components comprising software,hardware, or both without departing from the spirit of the presentdisclosure. In addition, where applicable, it is contemplated thatsoftware components can be implemented as hardware components, andvice-versa.

Software in accordance with the present disclosure, such asnon-transitory instructions, program code, and/or data, can be stored onone or more non-transitory machine readable mediums. It is alsocontemplated that software identified herein can be implemented usingone or more general purpose or specific purpose computers and/orcomputer systems, networked and/or otherwise. Where applicable, theordering of various steps described herein can be changed, combined intocomposite steps, and/or separated into sub-steps to provide featuresdescribed herein.

Embodiments described above illustrate but do not limit the invention.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the invention.Accordingly, the scope of the invention is defined only by the followingclaims.

What is claimed is:
 1. A radar system comprising: a radar unit adaptedto broadcast radar signals and receive return signals in responsethereto, the radar unit comprising: a waveform generator adapted toprovide pulse waveforms of different pulse widths and FrequencyModulated Continuous Wave (FMCW) waveforms, wherein the waveforms areinterleaved with each other to provide a predetermined repeatingtransmission sequence for the radar signals for detection of long rangeand short range targets, wherein the predetermined repeatingtransmission sequence comprises a first pulse transmission period fortransmission of one of the pulse waveforms of a first length, a secondpulse transmission period for transmission of one of the pulse waveformsof a second length, and a plurality of FMCW transmission periods fortransmission of the FMCW waveforms; a power amplifier adapted to amplifythe radar signals for broadcast; an antenna adapted to broadcast theradar signals and receive the return signals; and wherein the radar unitis adapted to detect the return signals in accordance with a detectionsequence comprising a first pulse detection period following the firstpulse transmission period, a second pulse detection period following thesecond pulse transmission period, and a plurality of FMCW detectionperiods interleaved with the FMCW transmission periods.
 2. The radarsystem of claim 1, further comprising a control unit adapted to adjustrise and fall times of the waveforms.
 3. The radar system of claim 2,wherein the control unit is a variable gain amplifier adapted to adjustthe rise and fall times of the waveforms to reduce side lobes and limita transmitted spectrum profile of the radar signals in response to acontrol signal.
 4. The radar system of claim 2, wherein the control unitis implemented by the waveform generator.
 5. The radar system of claim1, wherein the power amplifier is configured to receive a control signalto adjust the power amplifier in sympathy with the waveforms by turningoff the power amplifier in response to the control signal to preventsignal leakage from overloading other circuitry of the radar unit whenthe radar signals are not desired to be transmitted.
 6. The radar systemof claim 1, wherein the power amplifier is a Gallium Nitride (GaN) solidstate power amplifier.
 7. The radar system of claim 1, wherein thewaveform generator comprises an upconverter adapted to convert basebandsignals to provide the radar signals for amplification by the poweramplifier; wherein the radar unit further comprises a downconverteradapted to generate data signals based on the return signals; andwherein the upconverter and the downconverter are synchronized by ashared local oscillator signal to maintain phase coherence between theupconverter and the downconverter.
 8. The radar system of claim 1,wherein the waveform generator comprises: a phase locked loop (PLL)circuit and an oscillator adapted to provide the FMCW waveforms; and abaseband signal generator adapted to provide the pulse waveforms.
 9. Theradar system of claim 1, wherein the radar system further comprises aprocessor adapted to perform Doppler processing based on the returnsignals to determine velocities of targets reflecting the returnsignals.
 10. The radar system of claim 9, wherein the radar systemfurther comprises a base station separate from the radar unit andcomprising the processor.
 11. The radar system of claim 10, wherein theradar unit and the base station are both adapted to be located on awatercraft, wherein the radar unit is selectively detachable from thewatercraft by a user.
 12. A method of operating a radar system, themethod comprising: generating radar signals using a waveform generatorto provide pulse waveforms of different pulse widths and FrequencyModulated Continuous Wave (FMCW) waveforms, wherein the waveforms areinterleaved with each other to provide a predetermined repeatingtransmission sequence for the radar signals for detection of long rangeand short range targets, wherein the predetermined repeatingtransmission sequence comprises a first pulse transmission period fortransmission of one of the pulse waveforms of a first length, a secondpulse transmission period for transmission of one of the pulse waveformsof a second length, and a plurality of FMCW transmission periods fortransmission of the FMCW waveforms; amplifying the radar signals forbroadcast using a power amplifier; broadcasting the radar signals usingan antenna; receiving return signals at the antenna in response to theradar signals; detecting the return signals in accordance with adetection sequence comprising a first pulse detection period followingthe first pulse transmission period, a second pulse detection periodfollowing the second pulse transmission period, and a plurality of FMCWdetection periods interleaved with the FMCW transmission periods; andwherein the waveform generator, the power amplifier, and the antenna arepart of a radar unit.
 13. The method of claim 12, further comprisingadjusting rise and fall times of the waveforms using a control unit. 14.The method of claim 13, wherein the control unit is a variable gainamplifier adapted to adjust the rise and fall times of the waveforms toreduce side lobes and limit a transmitted spectrum profile of the radarsignals in response to a control signal.
 15. The method of claim 13,wherein the control unit is implemented by the waveform generator. 16.The method of claim 12, further comprising turning off the poweramplifier to adjust the power amplifier in sympathy with the waveformsin response to a control signal to prevent signal leakage fromoverloading other circuitry of the radar unit when the radar signals arenot desired to be transmitted.
 17. The method of claim 12, wherein thepower amplifier is a Gallium Nitride (GaN) solid state power amplifier.18. The method of claim 12, further comprising: converting basebandsignals to provide the radar signals for amplification by the poweramplifier using an upconverter of the waveform generator; generatingdata signals based on the return signals using a downconverter of theradar unit; and synchronizing the upconverter and the downconverter by ashared local oscillator signal to maintain phase coherence between theupconverter and the downconverter.
 19. The method of claim 12, whereinthe generating comprises: generating the FMCW waveforms using a phaselocked loop (PLL) circuit and an oscillator; and generating the pulsewaveforms using a baseband signal generator.
 20. The method of claim 12,further comprising performing Doppler processing based on the returnsignals to determine velocities of targets reflecting the returnsignals.
 21. The method of claim 20, wherein the Doppler processing isperformed by a processor of a base station separate from the radar unit.22. The method of claim 21, wherein the radar unit and the base stationare both adapted to be located on a watercraft, wherein the radar unitis selectively detachable from the watercraft by a user.
 23. The radarsystem of claim 10, further comprising a transmission interfaceconfigured to transmit radar data based on the return signals from theradar unit to the base station, wherein the radar unit and the basestation are not connected to each other by any wired or waveguidedsignal communications, and wherein the transmission interface is awireless interface configured to transmit the radar data as wirelesssignals.
 24. The method of claim 12, further comprising transmittingradar data based on the return signals from the radar unit to a basestation as wireless signals, wherein the radar unit and the base stationare not connected to each other by any wired or waveguided signalcommunications.